1. Field of the Invention
The present invention relates to an overflow speech detecting apparatus and, more particularly, to an overflow speech detecting apparatus used in a speech recognition system, for example, to determine whether input speech overflows or not.
2. Description of the Related Art
A conventional overflow detecting apparatus used in, e.g., a speech recognition system, compares the power level of a speech input signal with a given threshold value .theta.1, as shown in FIG. 1. In this method, if the power level exceeds the threshold value .theta.1, the apparatus determines speech overflow. In another method, as shown in FIG. 2, if the dynamic range of input speech in a speech recognition system is set to be 0 to .theta.2, an overflow detecting apparatus detects overflow speech if the power level of input speech exceeds the upper limit .theta.2 and an overflow occurs. If an overflow is detected by only checking whether an input power level exceeds the predetermined upper limit .theta.1 or .theta.2, overflow speech is determined even though the power level of the most part of input speech does not overflow like a pulse noise. In the case when the gain of the input speech signal is decreased in accordance with the determination, the power level of the overall input speech signal is lowered, and the power level feature pattern of the speech becomes ambiguous. In speech recognition, this leads to a decrease in recognition rate or accuracy.